1. Field of the Invention
The present invention relates generally to measuring angular position, and more particularly to sensing and encoding the angular position of a rotatably positionable object.
2. Description of the Background Art
Frequently, it is necessary or desirable to monitor the angular position of a rotatably positionable object, such as a rotating shaft. For example, numerous devices employ a rotating shaft driven by an electric motor to position device components according to the direction and amount of shaft rotation. Consequently, because the position of such components depends on the amount and direction of shaft rotation, a device may monitor the current position of a component by monitoring the angular position of the shaft.
A commonly used method of measuring the angular position of a rotatably positionable object is to use a slotted optical encoder. A conventional slotted optical encoder normally includes a very fine sheet of metal with elongated thin slots formed therein. The fine sheet of metal is then mounted on the rotatably positionable object such that it co-rotates therewith. A sensor, positioned on an opposite side of the metal sheet, detects and counts the pulses of light that pass through the thin slots as the object rotates.
A primary limitation of this method of measuring angular position is that it is expensive. Indeed, the cost of the thin sheet of slotted metal and of a sensor sufficiently sensitive to detect and count the light pulses passing through such thin slots is relatively high. Additionally, conventional slotted optical encoders also require an analog to digital (A/D) converter to convert the sensor readings to a digital signal for processing purposes. This requirement for an A/D converter further increases the cost of the slotted optical encoder approach.
Other conventional systems and methods for accurately and effectively measuring the angular position of a rotatably positionable object are typically either too fragile or too expensive to be commercially useful in many applications. Because electronic equipment is frequently transported from one location to another, it is desirable that such equipment be sufficiently rugged to withstand a reasonable degree of handling by transport personnel. Many types of electronic equipment must also withstand rough treatment by end users. In addition, it is also advantageous that the price of the angular position sensing components of a system not comprise a large portion of the cost of producing the system.
Accordingly, a need exists for a relatively inexpensive system and method for sensing the angular position of a rotatably positionable object. An additional need exists for an angular position sensing system and method that is robust and can withstand rough handling by users. Moreover, a need exists for a system and method for sensing the angular position of a rotatably positionable object that does not require an A/D converter.